Variable valve timing assembly for internal-combustion engines



3, 1 54 R. A. M sREGoR 2,685,281

VARIABLE VALVE TIMING ASSEMBLY FOR INTERNAL-COMBUSTION ENGINES 3Sheets-Sheet 1 Filed July 24, 1953 INVENTOR Rosem- A. Mm Gas BY Aug. 3,1954 Filed July 24, 1953 Tigf) 3 Sheets-Sheet 2 INVENTOR. Rosann- A.MAQGREGOP.

Aug. 3, 1954 R. VARIABLE VALVE T-IMI FOR INTERNAL-CGMBUST N ENGI S FiledJuly 24, 1953 3 Sheets-Sheet 3 f 32 m Ti S a, q G,

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r" 28 PZ 'WflWMv-fl A RNEYS Patented Aug. 3, 1954 (ygSTAT-ES PATENT,OFFICE VARIABLE VALVE TIMING ASSEMBLY FOR "'INTERNAIi-GOMBUSTIONENGINES Robert ArMacGregor, St. Paul, Minn.

- Ap'plicatiol'iJuly'24, 1953, Serial No. 370,006

. 2 Claims. 1 I :It is wellestablish'ed' that the valve timinginw'corporated in the design of a poppet valve internal :combustionengine as used: in anautomobile' is a compromise demanded by theflexibility requirements. Torque and performanceat low R. P.'M.

(anduhence, relatively low gas velocities, intake "and exhaust).callcforlate intake .and exhaust .valve opening short valve-opent overlap, and

hence short valve-open time. 1 At higher" gas "velocities; occurringconcurrently with high 3R. P. the engine performance can be muchimproved by earlier intake and exhaust valve "opening, longer:valve-open: period: and hence 'longer' valveeopen: overlap. 'If, then,thevalve timing 'couldi be advanced R. P. M. increase; andthe-'ivalve-open time lengthened, the .design "compromise presently re-:sorted to-would be eliminated, and substantial .iimprovementxin engineperformance would result.

in proportion to Thebroad object :of the present inventiontis' toprovide avalve timingmeans wherein the valve sftiming is varied in"the'manner discussed above,

: thus to achieve 7 the desirable :results noted.

. Summarized briefly, the zinvention comprises the'association,with-each engine cylinder, :of' two 1 pairs of valves, reachrpair1iincluding.:;one:zintake and one exhaust valve. Each pair iscontrolledby aiseparateLcam shaft,- and drive means for' the camshaftis:;:provided=, effective :to .advance'the opening of the intakezandexhaust valves'ofrone cam-shaft simultaneously withrcorresponding .re-

.atardation of'the opening of'z'the i iintakeifand exhaust.valvesofixthe'other "-cam shaft, said advancement and retardationoccurring in proportion to Pt.- P. .M.::-increases.

" A secondary object is to incorporate; inthe means for" efiecting thesimultaneous advancement andretardationof the cam shafts,acentrifugally. controlled drive transmittingrmeans .for 1 eachcamshaft, that can bexincorporated in present day engine designs with:minimum difficulty.

:Other objects will appear from the following description, the claimsappended thereto,.tand from the annexed drawings; in which likereference. characters designate like parts throughout a the severalviews,:and wherein:

- Figure 1 is a;view partly.in side elevationzand partly in longitudinalsection, through :aninternal: combustion :engine-iequipped with 'athe,variable valveiztiming-"means' constituting. the spresent invention;

Figure 2' is a planzsectionalview through said Figure 3 is agreatlyeniarg'edttransverse sec- .2 tionalview, throughone ofthe enginecylinders andits associated'valve means, taken substan- -tially online3-3 of Figure 1;

Figure 4 is anrenlarged transversev sectional :view online 4-4'ofFigure1, showing the drive "means for thecamshafts in front elevation; and

Figure 5 is a detail sectional view, the scale being enlarged stillfurther, of .one of-the cam shaft'drive mechanisms',ttaken on line 5- -5of Figure 4.

The reference. numeral 10 has been applied generally in the-drawings'to'an internal combustion engine, having atcylinder head l2,a'cylin- 'der block' Wand cylinders- 16.

"' disposedin side-by side relation, with both gears xbeing'inimesh:attheir peripherieswith a single i crank. shaft gear 28.7: Both cam:shaft gears .are,

ioftcourse, driven inf'the same direction, and as fshowniniFigure 4,timing marks can bevprovided on the crank shaft gear and on therespective icam shaftigears,rto insure-the proper positioning 1 'oftheseveral gears relative to one another.

' m-eans' of cam "shaft -shaft'w.

The means whereby rotation is transmitted to the respective cam shaftsisthe same in both instances, and hence; the'description of the drive"Hi will suffice for cam As will be'observed from'Figures 4-and 5, thecam shaft gear-'22 has a large-center opening 30,

and dispcsed diametrically opposite oneanother in communication withsaid center opening are worm wheel 'recesses32.

"Disposed within and substantially filling the center opening 30 is ahub 36 keyed'or otherwise secured-to the'cam" shaft 18 forrotationtherewith. A worm wheel shaft 38. has its ends en-'gaged"'i1ropposite ends of each recess 32, and

,, "rotating .on said worm wheel shaft is a Worm Wheel 40.

- Each of the diametrically opposite worm wheels #30 is iirmeshwithteeth-M formed in diametrically opposite','-- peripheral recesses ofthe hub *36. *'Since the worm-wheels'extend'into the recesses of the hubas well as into the recesses of the cam shaft gear, the worm wheelsinterengage the hub and gear for joint rotation.

Secured to each worm wheel 40, and projecting forwardly from the hub andcam shaft gear, are angular bob weights 44, said weights converging in adirection away from the worm wheels and being connected, intermediatetheir ends, by a spring 46.

By reason of the construction so far illustrated and described, it willbe apparent that on rotation of the crank shaft gear 28, the gears 22,24 will be rotated in the same direction. Through the interlockconstituted by the worm wheels, rotation of the hubs with the cam shaftgears will be effected.

As the R. P. M. of the engine increases, the bob weights #2 1 will swingoutwardly, in proportion to the number of revolutions per minute. Thespring it, of course, is used to balance the centrifugal forces actingupon the bob weights.

Movement of the bob weights dd outwardly from one another is effectiveto transmit rotational movement to the worm wheels, and rotationalmovement of the worm wheels will, in turn, be effective to rotate eachhub slightly relative to its associated cam shaft gear, due to themeshing of teeth :32 with the worm wheels.

It is important to note, in this regard, that the worm wheels associatedwith cam shaft 18 and cam shaft gear 22 are pitched in such a way as tocause the hub of one cam shaft to be rotated in one direction relativeto its associated cam shaft gear, and the hub of the other camshaft tobe rotated in an opposite direction relative to its associated cam shaftgear.

This arrangement is designed to effect the advance of one cam shaftsimultaneously with the retardation of the timing of the other camshaft, with the snnultaneous advance and retardation of the cam shaftsoccurring in direct ratio to the increase in revolutions per minute ofthe engine.

Referring to Figures 1 and 2, intake manifolds iii are provided at bothsides of the engine, and exhaust manifolds 5d are also provided at bothsides of the engine. The intake and exhaust manifolds at the left-handside of the engine are associated with the cam shaft and valves on thesame side, and correspondingly, the right-hand manifolds are associatedwith the right cam shaft and valves.

Spaced longitudinally of the right cam shaft is are intake valve earns52, one for each cylinder of the engine, and also spaced longitudinallyof the right cam shaft, and alternating with the intake valve cams, areexhaust valve cams 54.

The right-hand intake valve cams 52 control operation of the right-handintake valves 56, and the right-hand exhaust valve cams 5t controloperation of the right exhaust valves 58.

On the left cam shaft, left-hand intake valve cams Gil alternate withleft exhaust valve cams 62. As in the case of the right cam shaft andits associated valves, a pair of valve cams and valves is associatedwith each cylinder, with each pair of left-hand valves including oneintake and one exhaust valve.

The left-hand valves have been designated at (it, 65, the intake valvesbeing numbered 64 and the exhaust valves being numbered 65.

By reason of the construction illustrated and described, a predeterminedincrease in engine revolutions per minute, making desirable earlierintake and exhaust valve opening, and longer valve-open period resultingin longer valve-open overlap, will be translated into outward movementto a corresponding extent of the several bob weights of the respectivecam shafts. This will in turn be effective to advance the timing of theright cam shaft it, simultaneously with retardation of the timing of theleft cam shaft 20. As a result, the right intake and exhaust valves 56,58 Will open earlier than they will at lower engine speeds, and the leftintake and exhaust valves 64, 66 will open later than they will at saidlower engine speed. In this way, the cylinder has been opened earlier tothe intake system; and has been kept open to the intake system for alonger period of time. The same is true of the exhaust portion of thecycle. Engine performance is thus distinctly improved, and the necessityof setting the timing at a compromise location is obviated.

Of course, low revolutions per minute call for late intake and exhaustvalve opening, and short valve-open overlap resulting in shortvalve-open time. This adjusted timing results by reason of theconstruction illustrated and described, to accomplish the delayed intakeand exhaust valve opening and the shorter valve-open overlap.

It is of importance to note that in its basic aspects, the presentinvention is the variation of the valve timing in proportion to theincrease or reduction of revolutions per minute, to eliminate thecompromise settings heretofore required and, in the final analysis,improve engine performance. It is to be further observed that incarrying out this basic idea, I provide two pairs of valves percylinder, each pair being controlled by a separate cam shaft andincluding an intake and an exhaust valve, with said cam shafts being sodriven as to cause one cam shaft to be advanced in timing simultaneouslywith retardation of the other, responsively to changes in revolutionsper minute. The invention further embodies the timed opening and closingof the several valves associated with each cylinder, to cause coactionof the several valves in such a way as will produce longer or shortervalve-open overlap, depending on whether the engine is operating at highor low speed.

While the above constitutes the basic and essential invention, it is tobe noted that the invention further includes a specific means foreffecting the desired advancement and retardation of the respective camshafts, said means being centrifugally controlled at the location atwhich drive is transmitted to the cam shafts. The illustrated example ofsaid centrifugally controlled cam shaft drive mechanism, provided inFigures 4 and 5, is a presently preferred example of an advance-retarddevice that can be utilized in the inventive combination. It is be--lieved, however, that other designs may possibly be utilized, within thescope of the appended claims.

It is believed apparent that the invention is not necessarily confinedto the specific use or uses thereof described above, since it may beutilized for any purpose to which it may be suited. Nor is the inventionto be necessarily limited to the specific construction illustrated anddescribed, since such construction is only intended to be illustrativeof the principles of operation and the means presently devised to carryout said principles, it being considered that the invention comprehendsany minor change in construction that may be permitted within the scopeof the appended claims.

What is claimed is:

1. Variable valve timing means for internal combustion engines,comprising, in combination with an engine cylinder: two pairs of valvescontrolling the cylinder intake and exhaust with each pair including oneintake and one exhaust valve; a separate cam shaft for each pair ofvalves; and drive means for the respective cam shafts including acentrifugally controlled ad Vance for one of the cam shafts and acentrifugally controlled retard for the other cam shaft, for advancingthe opening of the valves of one pair simultaneously with retardation ofthe opening of the valves of the other pair, in proportion to changes inengine speed, said drive means including a centrally apertured cam shaftgear for each cam shaft, a hub disposed within the aperture of said gearand secured to the associated cam shaft, a worm wheel connecting the huband cam shaft for joint rotation, said worm wheel meshing with the huband cam shaft gear, and means secured to said worm wheel and respondingto centrifugal force to impart rotatable movement to the worm wheel, soas to partially rotate the hub relative to the cam shaft gear.

2. Variable valve timing means for internal combustion engines,comprising, in combination with an engine cylinder: two pairs of valvescontrolling the cylinder intake and exhaust with each pair including oneintake and one exhaust valve; a separate cam shaft for each pair ofvalves; and drive means for the respective cam shafts including acentrifugally controlled adgally controlled retard for the other camshaft, for advancing the opening of the valves of one pairsimultaneously with retardation of the opening of the valves of theother pair, in proportion to changes in engine speed, said drive meansincluding a centrally apertured cam shaft gear for each cam shaft, a hubdisposed within the aperture of said gear and secured to the associatedcam shaft, a worm wheel connecting the hub and cam shaft for jointrotation, said worm wheel meshing with the hub and cam shaft gear, andmeans secured to said worm wheel and responding to centrifugal force toimpart rotatable movement to the worm wheel, so as to partially rotatethe hub relative to the cam shaft gear, the worm wheels being arrangedfor rotation of the hub of one cam shaft in one dirertion simultaneouslywith rotation of the hub of the other cam shaft in an oppositedirection, relative to their associated cam shaft gears.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,318,542 Chevrolet Oct. 14, 1919 1,533,947 Riker Apr. 14,1925 1,654,366 Fedden et al Dec. 27, 1927 1,980,379 Burnett Nov. 13,1934 2,037,051 Smiley Apr. 14, 1936 2,057,354 Withers et a1. Oct. 13,1936

